Insulation has long been used to cover piping through which either hot or cold fluids flow.
Early efforts at insulating piping consisted of spreading cement in place on the exterior of the piping and pipe fitting and then adhering a fabric over the cement. Since then, insulation techniques have been developed that include various insulating materials, such as fiberglass covered with aluminum or plastic coverings. The aluminum and plastic covering are variously formed to take the shape of pipe lengths and pipe fittings.
The plastic coverings have generally been formed of commercial grade poly(vinyl chloride). Typically, the poly(vinyl chloride) used in coverings for pipe insulation has a specific gravity in the range of 1.44.
The poly(vinyl chloride) fittings have been formed into many shapes, some taking the shape of a Tee, an elbow or any other fitting to be covered. Others, such as described in U.S. Pat. No. 3,495,629 (Botsolas, Feb. 17, 1970) are designed with a first shape different from the fitting to be covered but with the capacity to be manipulated into a second shape in the form of the fitting to be covered.